The current volume in the EUI Law Department series of working papers results from the collaboration between the Department and the Finnish national Centre of Excellence Foundations of European Law and Polity, led by Professor Kaarlo Tuori of Helsinki University. Professors and researchers at the EUI Law Department have in a number of ways collaborated in the creation and operation of Foundations. Of present and former Professors of the Department, Miguel Poiares Maduro, Hans-W. Micklitz, Wojchiech Sadurski and Neil Walker have attended conferences by Foundations as speakers. It has been a valuable source of academic inspiration for me personally first to participate in the building-up and launch of Foundations while still at Åbo Akademi University in Finland, and then to engage in collaboration with the same Centre of Excellence after moving to the EUI as of September 2008. Law and Security - Facing the Dilemmas is a collection of papers emanating from so-called working group II within Foundations, headed by Professor Kimmo Nuotio of Helsinki University. As much of my own research, writing and teaching at the EUI is related to terrorism and counter-terrorism, it has fallen naturally to me to engage from the EUI side with the work done within Foundations. This collection of papers maps several dimensions of the multifaceted relationship between law and security, looking, inter alia, into issues related to the fight against terrorism, criminal law more generally, and the invocation of security among legitimate aims for the limitation of human rights. All authors are either members of Foundations or EUI researchers.